Mozilla Thunderbird and Firefox do not shows links correctly but coloured lines

Hello community!

Just wanted some important help on this issue please.

I've got some trouble with Mozilla Thunderbird, since it does not show the messages correctly when I receive them with links in the the form of images or just text. They're just shown like coloured lines although such links are functional (they are redirected to a new page in my explorer)
The same happens to my Mozilla, web pages are not shown correctly because the links objects are not shown well or the text links appears as coloured lines.
I'm a newbie since I've been trying Ubuntu for about a month and this seems to be a great thing to me. I like but this problem on Thunderbird and Firefox is infuriating. I've trying reinstalling both programs, disabling addons, etc, but the problem persists. Here you have some snapshots so you can get an idea on what's happening.